It has long been desired to maximize fuel economy, power and driveability in gasoline powered vehicles while enhancing acceleration, reducing emissions, and preventing hesitation. While it is known to enhance gasoline powered engine performance by employing dispersants to keep valves and fuel injectors clean in port fuel injection engines, such gasoline dispersants are not necessarily effective for cleaning up direct fuel injected engines. The reasons for this unpredictability may lie in the many mechanical and operational differences between the direct and port fuel injected engines and the fuels suitable for such engines.
With the current use of direct fuel injected gasoline engines, dispersants that previously could have been used for gasoline engines do not work for both direct injected engines and port fuel injected engines. For example Mannich dispersants that were used in port fuel injected gasoline engines fail to provide suitable improvement in direct injected gasoline engines.
Over the years, dispersant compositions for gasoline fuels have been developed. Dispersant compositions known in the art for use in fuels include compositions that may include polyalkylene succinimides, polyalkenepolyamines, polyetheramines, and polyalkyl substituted Mannich compounds. Dispersants are suitable for keeping soot and sludge suspended in a fluid, however dispersants are not particularly effective for cleaning surfaces once deposits have formed on the surfaces. Hence, fuel compositions for direct fuel injected engines often produce undesirable deposits in the engines. Accordingly, improved compositions that can prevent deposit build up, maintaining “as new” cleanliness for the vehicle life are desired. Ideally, the same composition that can clean up dirty fuel injectors restoring performance to the previous “as new” condition would be equally desirable and valuable in the attempt to reduce air borne exhaust emissions and to improve the power performance of the engines.
In accordance with the disclosure, exemplary embodiments provide a fuel composition for an internal combustion gasoline engine comprising, a method for improving performance of fuel injectors and a method for operating a direct fuel injected gasoline engine. The fuel composition includes a major amount of fuel and from about 5 to about 200 ppm by weight of a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. The amount of quaternary ammonium salt present in the fuel is sufficient to improve performance of a direct fuel injected engine having combusted the composition compared to the performance of such engine having combusted a fuel composition that does not contain the quaternary ammonium salt. The quaternary ammonium salt is a compound of the formula
wherein each of R1, R2, R3, and R4 is selected from a hydrocarbyl group containing from 1 to 25 carbon atoms, wherein at least one and not more than three of R1, R2, R3, and R4 is a hydrocarbyl group containing from 1 to 4 carbon atoms and at least one of R1, R2, R3, and R4 is a hydrocarbyl group containing from 8 to 25 carbon atoms, M− is selected from the group consisting of carboxylates, nitrates, nitrides, nitrites, hyponitrites, carbonates, and mixtures thereof, wherein the carboxylate is not an oxalate or formate.
Another embodiment of the disclosure provides a method of improving the injector performance of a direct fuel injected internal combustion gasoline engine. The method includes operating the engine on a fuel composition containing a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel of a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. The quaternary ammonium salt present in the fuel may improve injector performance by providing a reduction in LTFT of at least about 30%. The quaternary ammonium salt is a compound of the formula
wherein each of R1, R2, R3, and R4 is selected from a hydrocarbyl group containing from 1 to 25 carbon atoms, wherein at least one and not more than three of R1, R2, R3, and R4 is a hydrocarbyl group containing from 1 to 4 carbon atoms and at least one of R1, R2, R3, and R4 is a hydrocarbyl group containing from 8 to 25 carbon atoms, M− is selected from the group consisting of carboxylates, nitrates, nitrides, nitrites, hyponitrites, carbonates, and mixtures thereof, wherein the carboxylate is not an oxalate or formate.
A further embodiment of the disclosure provides a method of operating a direct fuel injected gasoline engine. The method includes combusting in the engine a fuel composition comprising a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel of a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. In further embodiments, the TGA weight loss is greater than 70 wt. %, such as greater than 80 wt. %, particularly greater than 90 wt. % weight loss. The quaternary ammonium salt is a compound of the formula
wherein each of R1, R2, R3, and R4 is selected from a hydrocarbyl group containing from 1 to 25 carbon atoms, wherein at least one and not more than three of R1, R2, R3, and R4 is a hydrocarbyl group containing from 1 to 4 carbon atoms and at least one of R1, R2, R3, and R4 is a hydrocarbyl group containing from 8 to 25 carbon atoms, M− is selected from the group consisting of carboxylates, nitrates, nitrides, nitrites, hyponitrites, carbonates, and mixtures thereof, wherein the carboxylate is not an oxalate or formate.
An advantage of the fuel additive described herein is that the additive may not only reduce the amount of deposits forming on direct fuel injectors, but the additive may also be effective to clean up dirty fuel injectors sufficient to provide improved engine performance.
Additional embodiments and advantages of the disclosure will be set forth in part in the detailed description which follows, and/or can be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.